Document proper usage and API

[nfantone]

Snippets found on README.md show examples of usage for a particular setup and doesn't showcase configuration options. Also, they don't work out of the box.

Another problem with the examples is that they somewhat contradict the following from the Getting Started guide on senecajs.org:

You export the plugin definition function and then call seneca.use with the name of the file. You can either require it in or if you like to be terse, let Seneca make the require call.

This doesn't hold true for this plugin as it expects the exported function of the module to be bound to the seneca instance:

module.exports = function(opts) {
    var seneca = this;
    var plugin = 'amqp-transport';
    var so = seneca.options();
    // ...

So, actually, you cannot require the module manually and must let seneca do that.

Anyway, this:

require('seneca')()
    .use(require('..'))
    .add({generate: 'id'}, function(message, done) {
        done(null, {pid: process.pid, id: '' + Math.random()});
    })
    .listen({type: 'amqp'});

Should really be something like:

require('seneca')()
      .use('seneca-amqp-transport', {
    amqp: {
      url: 'amqp://<username>:<password>@<hostname>:<port>'
    })
    .add({generate: 'id'}, function(message, done) {
        done(null, {pid: process.pid, id: '' + Math.random()});
    })
    .listen({type: 'amqp'});

[nfantone]

Documentation updated on #5.